1. Field of the Invention
The present invention relates to a device in which a load is supplied using alternating current (AC) power. More particularly, the present invention relates to an apparatus and method for controlling power supplied to a fixing unit to reduce an instantaneous heating time of the fixing unit and a flicker characteristic.
2. Description of the Related Art
A conventional fixing circuit for laser printers and photocopiers includes a controller for determining whether power is supplied to a fixing unit, a triac switching unit for supplying alternating current (AC) power to the fixing unit, and a triac driver for controlling the triac.
The conventional fixing circuit controller controls the fixing unit by receiving AC power from an input power supply and applying the AC power to components of the fixing unit. That is, the controller detects a temperature of the fixing unit using a temperature sensor, outputs a switch-on signal if it is determined that a temperature increase is needed, and applies the AC power to the fixing unit by activating the triac to an on-state at a zero-crossing time in every switching period using a photo triac in response to the switch-on signal.
As described above, in the conventional fixing circuit, since the controller simply controls the triac switching unit in order to control the temperature of the fixing unit, without having information on the AC power, such as information on a voltage synch angle of the AC power, irregular turn-on timing causes flickering of a display device using the same power source as an image forming device.
In addition, to reduce a print ready time, a supply of relatively high power may be needed in an initial warm-up of a fixing unit. However, this power increase causes an excessive inrush current, resulting in more pronounced flickering and a harmonic characteristic of the display device.
Accordingly, there is a need for an improved apparatus and method for controlling power supplied to a fixing unit.